Have you got last months Classic and Sports Car magazine?

[herecomestrouble]

If you have, have a look on the back cover.
There is a photo of the rear of an old race car with what looks like a disc brake fixed to the tail.
What is the car?
Is it a disc brake?
Why is it there?
Thanks. Paul

[Firefox1]

I think it's the Lotus 12 and the idea of the disc brake operating on the rear axle was to reduce unsprung weight (stands back ready to be shot down in flames).

[VetteG]

Didn't see the mag but this is a pic of a Lotus 12


G

[jamesatcandsc]

The only car I know that had that rear disc arrangement was a BRM P25/48 (if I recall correctly) and it could be that with most of its rear bodywork removed.
Seeing as the whole Ad is a tribute to Jo Bonnier, a BRM connection would make sense.
As for the question of why, who knows? BRM persevered with it longer than anyone had imagined and no one copied it, so it was obviously just a daft weight-saving idea that didn't come to anything on account of halving the rear's stopping power.

[nicanary]

Deffo the BRM - looked it up in my BRM book.

[herecomestrouble]

Thanks chaps. 1960 BRM it is. Just seems crazy to put it there.

[nicanary]

The single rear brake disc was a left-over from the previous model P25 front-engined car. When that was designed the single disc seemed a good idea - on braking heavily, 70% of the weight transfers to the front wheels, so 2 discs are required. But only 30% of weight on the rear means it only needs 1 disc.

When the rear-engined P48 was designed, they used cut-and-shut P25 chassis at first, so the running gear was left alone to reduce manufacturing costs. Not a particularly good idea, and soon dropped.